As it is known, internal combustion engines are equipped with a cooling circuit in which a pump driven by the crankshaft circulates a coolant fluid adapted to subtract heat from the engine, in use, to maintain the temperature of the engine components within an acceptable range of values. According to a conventional solution, the pump is permanently driven by the crankshaft, via a belt transmission, and therefore cannot be deactivated.
In motor vehicles, there is the problem of letting the engine reach a warmed-up condition as rapidly as possible after start up, for the two-fold purpose of reducing polluting emissions and allowing the engine to rapidly reach maximum efficiency.
For this purpose, there have recently been proposed actuating devices of the coolant fluid recirculation pump adapted to deactivate the pump at engine ignition until such warmed-up condition is reached.
A known solution consists in driving the pump by a first friction wheel that takes motion from the crankshaft and drives by rolling friction a second friction wheel fitted on the pump shaft. The first friction wheel is controlled by an actuator so that it can be disconnected from the second friction wheel.
However, the described device is somewhat complex, cumbersome and costly. In particular, it is quite difficult to provide a friction wheel device that allows to maintain the recirculation pump activated in the event of a failure to the electrical system or to the actuator, and therefore ensure engine operation.